Remove a note in the docs that no-one should care about anymore.

docs/src/userguide/early_binding_for_speed.rst

@@ -48,11 +48,6 @@ overheads. Consider this code:
 
 .. literalinclude:: ../../examples/userguide/early_binding_for_speed/rectangle_cpdef.pyx
 
-.. note::
-
-    In earlier versions of Cython, the :keyword:`cpdef` keyword is
-    ``rdef`` - but has the same effect.
-
 Here, we just have a single area method, declared as :keyword:`cpdef` to make it
 efficiently callable as a C function, but still accessible from pure Python
 (or late-binding Cython) code.